Doc / Book requests

[TwoClocks]

I just discovered this create, and I benchmarking my brains out. It's great. Thanks so much.

I've found a few things I wish there were docs for (or I can't find them). I would do a PR. Here is my list:

1. I couldn't figure out how to add another benchmark to the came crate. It took some trial and error to figure out I needed to copy the entire [[bench]] section in the Cargo.tomlto add a new entry.

2. Along the same lines, I have no idea what the harness = false does in the [[bench]] entry in the Cargo.toml file. I have no idea what other options are available here. It'd be nice to document that someplace.

3. This might be a bug, but if it isn't this should be documented. When using the advanced configuration and creating a group from scratch the ORDER OF CALLS to the group matter. For example, if you call measurment_time after you call bench_function the measurement time call is ignored and the default is used.

Thanks so much!

[lemmih]

Hi @TwoClocks. PRs for all three points would be most welcome.